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EP-2017-083

(Submitted on 20 May 2017)

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Abstract

A search is presented for long-lived particles with a mass between 25 and 50
GeV/$c^2$ and a lifetime between 2 and 500 ps, using proton-proton collision
data corresponding to an integrated luminosity of 2.0 fb$^{-1}$, collected by
the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are
assumed to be pair-produced in the decay of a 125 GeV/$c^2$ Standard-Model-like
Higgs boson. The experimental signature is a single long-lived particle,
identified by a displaced vertex with two associated jets. No excess above
background is observed and limits are set on the production cross-section as a
function of the mass and lifetime of the long-lived particle.

Figures and captions

Dijet invariant mass distribution in the different $ R_{xy}$ {} bins, for the 2011 data sample.
For illustration, the best fit with a signal $\pi_{\text{v}}$ {} model with mass \SI{35}{\GeVcc} and lifetime \SI{10}{\pico\second} is overlaid.
The solid blue line indicates the total background model,
the short-dashed green line indicates the signal model for signal strength $\mu=1$, and the long-dashed red line
indicates the best-fit signal strength.

Dijet invariant mass distribution in the different $ R_{xy}$ {} bins, for the 2012 data sample.
For illustration, the best fit with a signal $\pi_{\text{v}}$ {} model with mass \SI{35}{\GeVcc} and lifetime \SI{10}{\pico\second} is overlaid.
The solid blue line indicates the total background model,
the short-dashed green line indicates the signal model for signal strength $\mu=1$, and the long-dashed red line
indicates the best-fit signal strength.